Vulnerabilidades exploradas (CISA KEV)

In the Linux kernel, the following vulnerability has been resolved: ipv6: account for fraggap on the paged allocation path In __ip6_append_data(), when the paged-allocation branch is taken (MSG_MORE / NETIF_F_SG / large fraglen), alloclen and pagedlen are computed as alloclen = fragheaderlen + transhdrlen; pagedlen = datalen - transhdrlen; datalen already includes fraggap (datalen = length + fraggap). When fraggap is non-zero, this is not the first skb and transhdrlen is zero. The fraggap bytes carried over from the previous skb are copied just past the fragment headers in the new skb's linear area. The linear area is therefore undersized by fraggap bytes while pagedlen is overstated by the same amount, and the copy writes past skb->end into the trailing skb_shared_info. An unprivileged user can trigger this via a UDPv6 socket using MSG_MORE together with MSG_SPLICE_PAGES. The bad accounting was introduced by commit 773ba4fe9104 ("ipv6: avoid partial copy for zc"). Before commit ce650a166335 ("udp6: Fix __ip6_append_data()'s handling of MSG_SPLICE_PAGES"), the negative copy value caused -EINVAL to be returned. That later commit allowed MSG_SPLICE_PAGES to proceed in this case, making the corruption triggerable. The non-paged branch sets alloclen to fraglen, which already accounts for fraggap because datalen does. Bring the paged branch in line by adding fraggap to alloclen and subtracting it from pagedlen. After this adjustment, copy no longer collapses to -fraggap on the paged path, so remove the stale comment describing that old arithmetic. Since a negative copy is no longer expected for a valid MSG_SPLICE_PAGES case, remove the MSG_SPLICE_PAGES exception from the negative copy check.

In the Linux kernel, the following vulnerability has been resolved: netfilter: bridge: make ebt_snat ARP rewrite writable The ebtables SNAT target keeps the Ethernet source address rewrite behind skb_ensure_writable(skb, 0). This is intentional: at the bridge ebtables hooks the Ethernet header is addressed through skb_mac_header()/eth_hdr(), while skb->data points at the Ethernet payload. Asking skb_ensure_writable() for ETH_HLEN bytes would check the payload, not the Ethernet header, and would reintroduce the small packet regression fixed by commit 63137bc5882a. However, the optional ARP sender hardware address rewrite is different. It writes through skb_store_bits() at an offset relative to skb->data: skb_store_bits(skb, sizeof(struct arphdr), info->mac, ETH_ALEN) skb_header_pointer() only safely reads the ARP header; it does not make the later sender hardware address range writable. If that range is still held in a nonlinear skb fragment backed by a splice-imported file page, skb_store_bits() maps the frag page and copies the new MAC address directly into it. Ensure the ARP SHA range is writable before reading the ARP header and before calling skb_store_bits().

In the Linux kernel, the following vulnerability has been resolved: crypto: algif_aead - Revert to operating out-of-place This mostly reverts commit 72548b093ee3 except for the copying of the associated data. There is no benefit in operating in-place in algif_aead since the source and destination come from different mappings. Get rid of all the complexity added for in-place operation and just copy the AD directly.

In the Linux kernel, the following vulnerability has been resolved: posix-cpu-timers: fix race between handle_posix_cpu_timers() and posix_cpu_timer_del() If an exiting non-autoreaping task has already passed exit_notify() and calls handle_posix_cpu_timers() from IRQ, it can be reaped by its parent or debugger right after unlock_task_sighand(). If a concurrent posix_cpu_timer_del() runs at that moment, it won't be able to detect timer->it.cpu.firing != 0: cpu_timer_task_rcu() and/or lock_task_sighand() will fail. Add the tsk->exit_state check into run_posix_cpu_timers() to fix this. This fix is not needed if CONFIG_POSIX_CPU_TIMERS_TASK_WORK=y, because exit_task_work() is called before exit_notify(). But the check still makes sense, task_work_add(&tsk->posix_cputimers_work.work) will fail anyway in this case.

In the Linux kernel, the following vulnerability has been resolved: ALSA: usb-audio: Fix potential out-of-bound accesses for Extigy and Mbox devices A bogus device can provide a bNumConfigurations value that exceeds the initial value used in usb_get_configuration for allocating dev->config. This can lead to out-of-bounds accesses later, e.g. in usb_destroy_configuration.

In the Linux kernel, the following vulnerability has been resolved: ALSA: usb-audio: Fix out of bounds reads when finding clock sources The current USB-audio driver code doesn't check bLength of each descriptor at traversing for clock descriptors. That is, when a device provides a bogus descriptor with a shorter bLength, the driver might hit out-of-bounds reads. For addressing it, this patch adds sanity checks to the validator functions for the clock descriptor traversal. When the descriptor length is shorter than expected, it's skipped in the loop. For the clock source and clock multiplier descriptors, we can just check bLength against the sizeof() of each descriptor type. OTOH, the clock selector descriptor of UAC2 and UAC3 has an array of bNrInPins elements and two more fields at its tail, hence those have to be checked in addition to the sizeof() check.

In the Linux kernel, the following vulnerability has been resolved: media: uvcvideo: Skip parsing frames of type UVC_VS_UNDEFINED in uvc_parse_format This can lead to out of bounds writes since frames of this type were not taken into account when calculating the size of the frames buffer in uvc_parse_streaming.

In the Linux kernel, the following vulnerability has been resolved: net: fix __dst_negative_advice() race __dst_negative_advice() does not enforce proper RCU rules when sk->dst_cache must be cleared, leading to possible UAF. RCU rules are that we must first clear sk->sk_dst_cache, then call dst_release(old_dst). Note that sk_dst_reset(sk) is implementing this protocol correctly, while __dst_negative_advice() uses the wrong order. Given that ip6_negative_advice() has special logic against RTF_CACHE, this means each of the three ->negative_advice() existing methods must perform the sk_dst_reset() themselves. Note the check against NULL dst is centralized in __dst_negative_advice(), there is no need to duplicate it in various callbacks. Many thanks to Clement Lecigne for tracking this issue. This old bug became visible after the blamed commit, using UDP sockets.

A use-after-free vulnerability in the Linux kernel's netfilter: nf_tables component can be exploited to achieve local privilege escalation. The nft_verdict_init() function allows positive values as drop error within the hook verdict, and hence the nf_hook_slow() function can cause a double free vulnerability when NF_DROP is issued with a drop error which resembles NF_ACCEPT. We recommend upgrading past commit f342de4e2f33e0e39165d8639387aa6c19dff660.

It was discovered that a nft object or expression could reference a nft set on a different nft table, leading to a use-after-free once that table was deleted.

A flaw was found in the Linux kernel, where unauthorized access to the execution of the setuid file with capabilities was found in the Linux kernel’s OverlayFS subsystem in how a user copies a capable file from a nosuid mount into another mount. This uid mapping bug allows a local user to escalate their privileges on the system.

A use after free vulnerability exists in the ALSA PCM package in the Linux Kernel. SNDRV_CTL_IOCTL_ELEM_{READ|WRITE}32 is missing locks that can be used in a use-after-free that can result in a priviledge escalation to gain ring0 access from the system user. We recommend upgrading past commit 56b88b50565cd8b946a2d00b0c83927b7ebb055e

An out-of-bounds (OOB) memory write flaw was found in the Linux kernel’s watch_queue event notification subsystem. This flaw can overwrite parts of the kernel state, potentially allowing a local user to gain privileged access or cause a denial of service on the system.

A flaw was found in the way the "flags" member of the new pipe buffer structure was lacking proper initialization in copy_page_to_iter_pipe and push_pipe functions in the Linux kernel and could thus contain stale values. An unprivileged local user could use this flaw to write to pages in the page cache backed by read only files and as such escalate their privileges on the system.

A vulnerability was found in the Linux kernel’s cgroup_release_agent_write in the kernel/cgroup/cgroup-v1.c function. This flaw, under certain circumstances, allows the use of the cgroups v1 release_agent feature to escalate privileges and bypass the namespace isolation unexpectedly.

A heap-based buffer overflow flaw was found in the way the legacy_parse_param function in the Filesystem Context functionality of the Linux kernel verified the supplied parameters length. An unprivileged (in case of unprivileged user namespaces enabled, otherwise needs namespaced CAP_SYS_ADMIN privilege) local user able to open a filesystem that does not support the Filesystem Context API (and thus fallbacks to legacy handling) could use this flaw to escalate their privileges on the system.

A double free bug in packet_set_ring() in net/packet/af_packet.c can be exploited by a local user through crafted syscalls to escalate privileges or deny service. We recommend upgrading kernel past the effected versions or rebuilding past ec6af094ea28f0f2dda1a6a33b14cd57e36a9755

A heap out-of-bounds write affecting Linux since v2.6.19-rc1 was discovered in net/netfilter/x_tables.c. This allows an attacker to gain privileges or cause a DoS (via heap memory corruption) through user name space

In the Linux kernel before 5.1.17, ptrace_link in kernel/ptrace.c mishandles the recording of the credentials of a process that wants to create a ptrace relationship, which allows local users to obtain root access by leveraging certain scenarios with a parent-child process relationship, where a parent drops privileges and calls execve (potentially allowing control by an attacker). One contributing factor is an object lifetime issue (which can also cause a panic). Another contributing factor is incorrect marking of a ptrace relationship as privileged, which is exploitable through (for example) Polkit's pkexec helper with PTRACE_TRACEME. NOTE: SELinux deny_ptrace might be a usable workaround in some environments.

An integer overflow flaw was found in the Linux kernel's create_elf_tables() function. An unprivileged local user with access to SUID (or otherwise privileged) binary could use this flaw to escalate their privileges on the system. Kernel versions 2.6.x, 3.10.x and 4.14.x are believed to be vulnerable.

Linux distributions that have not patched their long-term kernels with https://git.kernel.org/linus/a87938b2e246b81b4fb713edb371a9fa3c5c3c86 (committed on April 14, 2015). This kernel vulnerability was fixed in April 2015 by commit a87938b2e246b81b4fb713edb371a9fa3c5c3c86 (backported to Linux 3.10.77 in May 2015), but it was not recognized as a security threat. With CONFIG_ARCH_BINFMT_ELF_RANDOMIZE_PIE enabled, and a normal top-down address allocation strategy, load_elf_binary() will attempt to map a PIE binary into an address range immediately below mm->mmap_base. Unfortunately, load_elf_ binary() does not take account of the need to allocate sufficient space for the entire binary which means that, while the first PT_LOAD segment is mapped below mm->mmap_base, the subsequent PT_LOAD segment(s) end up being mapped above mm->mmap_base into the are that is supposed to be the "gap" between the stack and the binary.