What is CVE-2026-25920?

CVE-2026-25920 is a medium-severity vulnerability in Sumatrapdfreader Sumatrapdf, classified under Out-of-bounds Read. CVSS score: 5.5/10. Published 2026-02-09.

How severe is CVE-2026-25920?

Medium severity. CVSS v3 base score is 5.5 out of 10.

Out-of-bounds Read in Sumatrapdfreader Sumatrapdf

CVE-2026-25920

SumatraPDF is a multi-format reader for Windows. In 3.5.2 and earlier, a heap out-of-bounds read vulnerability exists in SumatraPDF's MOBI HuffDic decompressor. The bounds check in AddCdicData() only validates half the range that DecodeOne() actually accesses. Opening a crafted .mobi file can read nearly (1 << codeLength) bytes beyond the CDIC dictionary buffer, leading to a crash.

Vulnerability class: Buffer Overflow

Published 2026-02-09 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 5.5 (Medium). Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H.

EPSS exploit prediction

EPSS: 0.002 (12.9th percentile), scored 2026-09-29.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 13th percentile — 12.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.002 · newest: 0.002 · change: +0.000

Affected products

Sumatrapdfreader Sumatrapdf — versions <= 3.5.2

Weakness classification (CWE)

CWE-125 — Out-of-bounds Read

References

github.com/sumatrapdfreader/sumatrapdf/security/advisories/GHSA-5mwx-65x7-cffp (Exploit, Vendor Advisory)
github.com/sumatrapdfreader/sumatrapdf/commit/12b6887e9dfff874fe8749bab1bdc53d4… (Product)
github.com/sumatrapdfreader/sumatrapdf/blob/916392f94bc34e24f3c3286893ac6d7fa1e… (Product)

Frequently asked questions

What is CVE-2026-25920?: CVE-2026-25920 is a medium-severity vulnerability in Sumatrapdfreader Sumatrapdf, classified under Out-of-bounds Read. CVSS score: 5.5/10. Published 2026-02-09.
How severe is CVE-2026-25920?: Medium severity. CVSS v3 base score is 5.5 out of 10.