SAIL: WebP decoder division by zero through malformed animated canvas metadata

published 2026-10-28 12 d ago modified 2026-10-29 10 d ago also EUVD-2026-112083

cvss: 4.8; version 4.0, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.1%; EPSS 0.1% chance of exploitation in 30 days, percentile 2%
public exploits: 0; none known

SAIL is a cross-platform library for loading and saving images with support for animation, metadata, and ICC profiles. Prior to version 1.0.2, the built-in WebP decoder can crash during loader initialization when processing a malformed animated WebP file with inconsistent container or `ANMF` frame metadata. In `sail_codec_load_init_v8_webp()` in `src/sail-codecs/webp/webp.c`, `WebPDemuxGetI` with `WEBP_FF_CANVAS_WIDTH` can return a zero `image_local->width`, which is then used as a divisor when calculating `bytes_per_pixel` from the image row size. The division happens before frame decoding and before generic image skeleton validation in `src/sail/sail_advanced.c`, causing an arithmetic fault and process termination. Applications accepting untrusted WebP images can consequently suffer denial of service; builds must include the affected WebP codec. This issue is fixed in version 1.0.2.

Patch / fix

fixed in 1 distros 1 links 1

sail sail 1.0.2

sail Debian 14 1.2.0-1

debian advisories DEBIAN-CVE-2026-59959

github.com/HappySeaFox/sail@4956601 commit

CISA SSVC

Exploitation: Proof of concept is public
Automatable: no
Technical impact: partial
Assessed: 10 d ago (2026-10-29)

Exploit prediction

0.13% chance of exploitation in the next 30 days, higher than 2% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

github.com https://github.com/HappySeaFox/sail/security/advisories/GHSA-5g8g-g347-84m8 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
CNA	4.0	4.8	CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
CNA	4.0	4.8	CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Affected products

HappySeaFox sail

Classification

Weakness

CWE-369 Divide By Zero

References

Sources

CVE List CVE-2026-59959
NVD CVE-2026-59959

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.

Summary