VulnerabilityPublished 29 Oct 2026

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

Affects pillowSource GCVE Database

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Authoritative record:CVE-2026-96638· Medium 6.5

Not known to be exploited · CVSS 6.5 Medium : upgrade to 13.0.0 when convenient.

Data as of 29 Oct 2026, 13:06 UTC

CVSS 3.1 base score

6.5Medium

How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none

CVSS scores by source
CNA (GitHub_M)	CVSS 3.1	6.5

Patch: Available – fixed in 13.0.0

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: Required
Scope: Unchanged
Confidentiality: None
Integrity: None
Availability: High

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: Required: Successful exploitation of this vulnerability requires a user to take some action before the vulnerability can be exploited.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 21 Oct 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade pillow to 13.0.0.

Patches and advisories

github.com/python-pillow/Pillow/commit/e7794835e323ff2691d9b3a974cade1a44301b9a (opens in a new tab)

Affected software

Product	Affected	Fixed in
Bitnamipillow`pkg:bitnami/pillow`Other threats	Affected >=9.1.0 <13.0.0	Fixed in 13.0.0

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Upgrade Pillow to version 13.0.0 or later, where this vulnerability is fixed. The vendor has released an official patch (commit e7794835e323ff2691d9b3a974cade1a44301b9a) addressing this issue. No other mitigations are indicated.

Description

A vulnerability in the Pillow Python imaging library versions 9.1.0 through 12.x allows crafted BMP RLE images to cause excessive memory allocation during decoding. This memory amplification can lead to denial of service by exhausting system memory. The issue is fixed in version 13.0.0.

Impact

An attacker can craft a malicious BMP image that triggers excessive memory allocation during decoding, potentially causing the application or system to run out of memory and crash or become unresponsive. This is a denial of service impact. There is no indication of code execution or data corruption from the provided data.

Summary

Pillow versions from 9.1.0 up to but not including 13.0.0 contain a flaw in the BmpRleDecoder.decode() function within src/PIL/BmpImagePlugin.py. Specifically, crafted BMP files using RLE delta escapes and absolute-mode runs can cause the decoder to append data beyond the expected destination length without limiting the amount per branch. A single delta can add approximately 255 image rows in one iteration, which can cause a small BMP file to expand its data buffer to hundreds of megabytes or more. This results in memory exhaustion and a denial of service condition. The vulnerability is addressed in Pillow 13.0.0.

References

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