CVE-2021-22898 — curl 7.7 through 7.76.1 suffers from an information disclosure when the `-t` command line option,...
curl 7.7 through 7.76.1 suffers from an information disclosure when the `-t` command line option, known as `CURLOPT_TELNETOPTIONS` in libcurl, is used to send variable=content pairs to TELNET servers. Due to a flaw in the option parser for sending NEW_ENV variables, libcurl could be made to pass on uninitialized data from a stack based buffer to the server, resulting in potentially revealing sensitive internal information to the server using a clear-text network protocol.
Who exploits it and how urgent it is
A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.
How the score was calculated
- EPSS 4.5% (30-day exploitation probability)+14
- CISA SSVC: exploitation "poc"+5
The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).
Triage
Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.
CISA SSVC assessment CISA
Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.
Remediation
Fixes and mitigations documented by the sources — linked to the original advisory.
- Documented patch — www.openwall.com (NIST National Vulnerability Database)
- Documented patch — cert-portal.siemens.com (NIST National Vulnerability Database)
- Documented patch — curl.se (NIST National Vulnerability Database)
- Documented patch — github.com (NIST National Vulnerability Database)
- Documented patch — hackerone.com (NIST National Vulnerability Database)
- Documented patch — www.oracle.com (NIST National Vulnerability Database)
- Documented patch — www.oracle.com (NIST National Vulnerability Database)
- Documented patch — www.oracle.com (NIST National Vulnerability Database)
First 24 hours
Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.
- Identify exposed assets running the affected vendor/product/version combinations (Debian Debian Linux, Fedoraproject Fedora, Haxx Curl…).
- The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
- Apply the fixed version or the patch documented under Remediation.
- Exploitation requires user interaction: tighten email/web filtering and warn affected users.
- EPSS ahead of 91% of scored CVEs: prioritize it in the patch queue.
- Search available logs for exploit probes matching the vulnerability class (memory corruption), errors and authentication anomalies.
Affected scope
Vendor, product and versions as the sources word them.
| Vendor | Product | Versions | Status | Source |
|---|---|---|---|---|
| Debian | Debian Linux | version 9.0 | Vulnerable | NIST National Vulnerability Database |
| Fedoraproject | Fedora | version 34version 33 | Vulnerable | NIST National Vulnerability Database |
| Haxx | Curl | ≥ 7.7 and ≤ 7.76.1 | Vulnerable | NIST National Vulnerability Database |
| Oracle | Communications Cloud Native Core Binding Support Function | version 1.11.0 | Vulnerable | NIST National Vulnerability Database |
| Oracle | Communications Cloud Native Core Network Function Cloud Native Environment | version 1.10.0 | Vulnerable | NIST National Vulnerability Database |
| Oracle | Communications Cloud Native Core Network Repository Function | version 1.15.0version 1.15.1 | Vulnerable | NIST National Vulnerability Database |
| Oracle | Communications Cloud Native Core Network Slice Selection Function | version 1.8.0 | Vulnerable | NIST National Vulnerability Database |
| Oracle | Communications Cloud Native Core Service Communication Proxy | version 1.15.0 | Vulnerable | NIST National Vulnerability Database |
| Oracle | Essbase | < 11.1.2.4.047≥ 21.0 and < 21.3 | Vulnerable | NIST National Vulnerability Database |
| Oracle | Mysql Server | < 5.7.34≥ 8.0.15 and < 8.0.25 | Vulnerable | NIST National Vulnerability Database |
| Siemens | Sinec Infrastructure Network Services | < 1.0.1.1 | Vulnerable | NIST National Vulnerability Database |
| Splunk | Universal Forwarder | ≥ 8.2.0 and < 8.2.12≥ 9.0.0 and < 9.0.6version 9.1.0 | Vulnerable | NIST National Vulnerability Database |
Attack characteristics
The CVSS vector, decoded. It describes the attack, not your exposure to it.
Every base score collected
Sources score independently and may disagree; each row says who scored it and under which version.
| Score | Version | Severity | Expl. | Impact | Scored by |
|---|---|---|---|---|---|
| 3.1 | CVSS 3.1 | Low | 1.6 | 1.4 | nvd@nist.gov via NIST National Vulnerability Database |
| 3.1 | CVSS 3.1 | Low | 1.6 | 1.4 | 134c704f-9b21-4f2e-91b3-4a467353bcc0 via NIST National Vulnerability Database |
| 3.1 | CVSS 3.1 | Low | — | — | GitHub, Inc. via GitHub Security Advisories |
| 3.1 | CVSS 3.1 | Low | — | — | CISA-ADP via CVE Program (cve.org) e CISA ADP |
| 2.6 | CVSS 2.0 | Low | 4.9 | 2.9 | nvd@nist.gov via NIST National Vulnerability Database |
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:N/A:N (score shown at the top: nvd@nist.gov) Weakness MITRE
Weakness class according to MITRE’s CWE catalog.
EPSS over time FIRST
Oct 13, 2026 → Oct 15, 2026 · 3 reading(s) · max 4.51%
Detection
Read off the CVSS vector and the weakness class. Starting points, not tested rules.
- Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
- Correlate service crashes/restarts with inbound traffic; repeated crashes may indicate attempts.
Timeline
What happened to this CVE, newest first.
- 2026
- SSVC assessment updated
- Record published
- Fix documented
- Affected products added · haxx/curl, debian/debian linux, fedoraproject/fedora, oracle/communications cloud native core binding support function,
- CVSS changed · 3.1
- Source status changed · → Modified
- Record created in this database
- 2021
- CVE published
Source activity
Repeated readings are counted rather than listed.
- 2× References added · Oct 14, 2026 – Oct 14, 2026
- 1× Official description updated · Oct 14, 2026 – Oct 14, 2026
References
22 on the record
- www.oracle.com//security-alerts/cpujul2021.html
- curl.se/docs/CVE-2021-22898.html
- hackerone.com/reports/1176461
- github.com/curl/curl/commit/39ce47f219b09c380b81f89fe54ac586c8db6bde
- www.openwall.com/lists/oss-security/2021/07/21/4
- www.oracle.com/security-alerts/cpuapr2022.html
- cert-portal.siemens.com/productcert/pdf/ssa-389290.pdf
- www.oracle.com/security-alerts/cpujan2022.html
- lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/POOC
- www.debian.org/security/2022/dsa-5197
- lists.debian.org/debian-lts-announce/2022/08/msg00017.html
- github.com/advisories/GHSA-7w8r-q58w-5wcr
- lists.apache.org/thread.html/rc713534b10f9daeee2e0990239fa407e2118e4aa9e88a7041177497c
- cert-portal.siemens.com/productcert/html/ssa-398330.html
- lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/FRUC
- nvd.nist.gov/vuln/detail/CVE-2021-22898
- lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/POOC
- lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/POOC3U
- lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/FRUCW2
- lists.apache.org/thread.html/rc713534b10f9daeee2e0990239fa407e2118e4aa9e88a7041177497c
- lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/FRUC
- lists.debian.org/debian-lts-announce/2021/08/msg00017.html
Elsewhere on this site
Related CVEs (same products)
- High CVE-2026-82208 wolfSSL CA-cache hit overrides callback Sep 6, 2026
- High CVE-2026-80229 OpenSSL provider use-after-free Sep 6, 2026
- High CVE-2026-80230 OpenSSL pinning bypass Sep 6, 2026
- High CVE-2026-80231 native CA store conn reuse Sep 6, 2026
- High CVE-2026-80255 secure cookie attribute bypass with tab Sep 6, 2026
- High CVE-2026-82209 domain-scoped PSL domain cookie Sep 6, 2026
Not in any source we poll
Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.
- No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
- No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
- No exploit packet captures, log samples, or incident case IDs supplied.
Answered from this record
Text assembled only from the fields above — no additional claims.
What should defenders know first?
CVE-2021-22898 is "curl 7.7 through 7.76.1 suffers from an information disclosure when the `-t` command line option,...", rated Low. It affects Debian Linux (Debian); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 3.1 describes technical severity. EPSS 4.51% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.
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