CVE Intelligence
Medium Denial of service

CVE-2026-96638 — Pillow: BMP RLE decoder memory-amplification DoS via unbounded delta escape / absolute mode

Pillow is a Python imaging library. From 9.1.0 until 13.0.0, BmpRleDecoder.decode() in src/PIL/BmpImagePlugin.py permits crafted RLE BMP delta escapes and absolute-mode runs to append beyond the remaining dest_length without a per-branch cap. A delta can add roughly 255 image rows in one iteration, so a kilobyte-sized file with a large but permitted width can expand the data bytearray to hundreds of megabytes or more, causing memory-exhaustion denial of service. This issue is fixed in version 13.0.0.

Published Oct 21, 2026 · Updated Oct 28, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP, GitHub Security Advisories · CNA: GitHub_M

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.
How the score was calculated
  • EPSS 0.3% (30-day exploitation probability)+4
  • Technical severity (medium)+3

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.

Exploitation
Not confirmed
Not in CISA KEV — an absence of record, not proof it is unexploited.
EPSS FIRST
0.35%
ahead of 28% of scored CVEs · Oct 30, 2026
Affects
Python
Pillow
CVSS base
6.5
Medium · 3 source(s)

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.

Exploitation
None
none · proof-of-concept · active
Automatable
No
can an attacker script the kill-chain steps
Technical impact
Partial
partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

  • Documented patch — github.com (NIST National Vulnerability Database)
  • Pip Pillow: fixed in version 13.0.0 — github.com (GitHub Security Advisories)

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.

  1. Identify exposed assets running the affected vendor/product/version combinations (Python Pillow, Python-pillow Pillow, Pip Pillow).
  2. The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
  3. Apply the fixed version or the patch documented under Remediation.
  4. Exploitation requires user interaction: tighten email/web filtering and warn affected users.
  5. Search available logs for exploit probes matching the vulnerability class (denial of service), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

VendorProductVersionsStatusSource
Python Pillow ≥ 9.1.0 and < 13.0.0 Vulnerable NIST National Vulnerability Database
Python-pillow Pillow version >= 9.1.0, < 13.0.0 Vulnerable CVE Program (cve.org) e CISA ADP
Pip Pillow ≥ 9.1.0 and < 13.0.0 Vulnerable GitHub Security Advisories

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
Required
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

ScoreVersionSeverityExpl.ImpactScored by
6.5 CVSS 3.1 Medium 2.8 3.6 security-advisories@github.com via NIST National Vulnerability Database
6.5 CVSS 3.1 Medium — — GitHub, Inc. via GitHub Security Advisories
6.5 CVSS 3.1 Medium — — GitHub_M via CVE Program (cve.org) e CISA ADP
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H (score shown at the top: security-advisories@github.com)

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-400 · Uncontrolled Resource Consumption

Other CVEs with this weakness →

EPSS over time FIRST

Oct 22, 2026 → Oct 30, 2026 · 9 reading(s) · max 0.35%

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).
  • Track CPU/memory spikes and availability drops correlated with request patterns.
web/proxy/WAF logsnetwork IDS/IPSresource metrics

Timeline

What happened to this CVE, newest first.

  • 2026
  • SSVC assessment updated
    Oct 28, 2026 · CVE Program (cve.org) e CISA ADP
  • Fix documented
    Oct 27, 2026 · NIST National Vulnerability Database
  • Affected products added · python/pillow
    Oct 27, 2026 · NIST National Vulnerability Database
  • Source status changed · Undergoing Analysis → Analyzed
    Oct 27, 2026 · NIST National Vulnerability Database
  • Source status changed · Awaiting Analysis → Undergoing Analysis
    Oct 23, 2026 · NIST National Vulnerability Database
  • Fix documented
    Oct 22, 2026 · GitHub Security Advisories
  • Affected products added · pip/pillow
    Oct 22, 2026 · GitHub Security Advisories
  • Source status changed · Received → Awaiting Analysis
    Oct 22, 2026 · NIST National Vulnerability Database
  • Affected products added · python-pillow/pillow
    Oct 21, 2026 · CVE Program (cve.org) e CISA ADP
  • Record published
    Oct 21, 2026
  • CVSS changed · 6.5
    Oct 21, 2026 · NIST National Vulnerability Database
  • Source status changed · → Received
    Oct 21, 2026 · NIST National Vulnerability Database
  • Record created in this database
    Oct 21, 2026 · Alertas do Telegram
  • CVE published
    Oct 21, 2026 · GitHub_M

Source activity

Repeated readings are counted rather than listed.

  • 2× References added · Oct 21, 2026 – Oct 22, 2026
  • 1× Official description updated · Oct 21, 2026 – Oct 21, 2026

References

6 on the record

Elsewhere on this site

Python
every CVE for this vendor
Denial of service
same class
CWE-400
other pages naming this weakness

Related CVEs (same products)

  • CVE-2026-114501 Pillow: Arrow export leaks stale heap memory when PILLOW_ALIGNMENT > 1 10d
  • CVE-2026-96778 Pillow: Heap buffer overflow writing JPEG comment after ICC profile fills buffer 10d
  • CVE-2026-96640 Pillow PDF append accepts malformed shared page-tree DAG causing resource exhaustion 10d
  • CVE-2026-96641 Pillow: Reachable undefined behavior in native integer operations, potentially leading to denial of service or logic integrity compromise 10d
  • CVE-2026-96642 Pillow: TarIO negative size field causes infinite CPU-spin loop 10d
  • CVE-2026-96644 Pillow: Heap over-read in WMF/EMF rendering via 16-bit dimension truncation (Windows builds) 10d

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-2026-96638 is "Pillow: BMP RLE decoder memory-amplification DoS via unbounded delta escape / absolute mode", rated Medium. It affects Pillow (Python); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 6.5 describes technical severity. EPSS 0.35% 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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