Cyber Posture

CVE-2026-26740

HighPublic PoC

Published: 18 March 2026

Published
18 March 2026
Modified
21 March 2026
KEV Added
—
Patch
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CVSS Score 8.2 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H
EPSS Score 0.0021 42.4th percentile
Risk Priority 17 60% EPSS · 20% KEV · 20% CVSS

Description

Buffer Overflow vulnerability in giflib v.5.2.2 allows a remote attacker to cause a denial of service via the EGifGCBToExtension overwriting an existing Graphic Control Extension block without validating its allocated size.

Mitigating Controls (NIST 800-53 r5)AI

SI-2 Flaw Remediation good match
prevent

Directly mitigates the buffer overflow in giflib by requiring timely remediation through patching or upgrading to a version that validates allocated size in EGifGCBToExtension.

SI-16 Memory Protection good match
prevent

Implements memory protection mechanisms such as address space layout randomization and data execution prevention that thwart exploitation of the heap buffer overflow leading to corruption and crashes.

SI-10 Information Input Validation partial match
prevent

Requires validation of GIF input sizes and structures before processing with giflib, reducing the risk of triggering the unvalidated overwrite in EGifGCBToExtension.

Security SummaryAI

CVE-2026-26740 is a buffer overflow vulnerability (CWE-787) affecting giflib version 5.2.2. The flaw resides in the EGifGCBToExtension function, which allows overwriting an existing Graphic Control Extension block without validating its allocated size, potentially leading to heap corruption. Published on 2026-03-18, it carries a CVSS v3.1 base score of 8.2 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H).

A remote attacker can exploit this vulnerability over the network with low attack complexity, requiring no privileges or user interaction. Exploitation triggers a denial of service through application crashes due to the unvalidated buffer overwrite, alongside limited integrity impacts such as potential data tampering, but no confidentiality loss.

A proof-of-concept demonstrating the heap out-of-bounds write via gce_len in giflib giftool is available at https://github.com/zakkanijia/POC/blob/main/giflib/giftool/giflib_giftool_gce_len_heap_oobwrite_disclosure.md. No official advisories or patches are detailed in the provided references.

Details

CWE(s)
CWE-787

Affected Products

giflib project
giflib
5.2.2

MITRE ATT&CK Enterprise TechniquesAI

T1190 Exploit Public-Facing Application Initial Access
Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.
attack.mitre.org →
T1499.004 Application or System Exploitation Impact
Adversaries may exploit software vulnerabilities that can cause an application or system to crash and deny availability to users.
attack.mitre.org →
Why these techniques?

Remote buffer overflow in giflib enables exploitation of public-facing applications (T1190) and application crashes via exploitation (T1499.004).

Confidence: HIGH · MITRE ATT&CK Enterprise v19.0

References