How severe is CVE-2026-23951?

CVE-2026-23951 has a CVSS 3.x base score of 5.5, rated medium severity. It is exploitable over local access with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2026-23951 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (9th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-23951?

CVE-2026-23951 affects Sumatrapdfreader Sumatrapdf. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-23951?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2026-23951 have an EU (EUVD) identifier?

Yes. CVE-2026-23951 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-4205.

When was CVE-2026-23951 published?

CVE-2026-23951 was published on 2026-01-22 and last updated on 2026-06-17.

CVE-2026-23951

CVE-2026-23951 is a medium-severity vulnerability in Sumatrapdfreader Sumatrapdf with a CVSS 3.x base score of 5.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-193.

Key facts

Severity: Medium (CVSS 3.x base score 5.5)
EPSS exploit prediction: 0% (9th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-4205
Weakness: CWE-193
Affected product: Sumatrapdfreader Sumatrapdf
Published: 2026-01-22
Last modified: 2026-06-17

Description

SumatraPDF is a multi-format reader for Windows. All versions contain an off-by-one error in the validation code that only triggers with exactly 2 records, causing an integer underflow in the size calculation. This bug exists in PalmDbReader::GetRecord when opening a crafted Mobi file, resulting in an out-of-bounds heap read that crashes the app. There are no published fixes at the time of publication.

Frequently asked questions

What is CVE-2026-23951?: SumatraPDF is a multi-format reader for Windows. All versions contain an off-by-one error in the validation code that only triggers with exactly 2 records, causing an integer underflow in the size calculation. This bug exists in PalmDbReader::GetRecord when opening a crafted Mobi file, resulting in an out-of-bounds heap read that crashes the app. There are no published fixes at the time of publication.
How severe is CVE-2026-23951?: CVE-2026-23951 has a CVSS 3.x base score of 5.5, rated medium severity. It is exploitable over local access with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2026-23951 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (9th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-23951?: CVE-2026-23951 affects Sumatrapdfreader Sumatrapdf. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-23951?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-23951 have an EU (EUVD) identifier?: Yes. CVE-2026-23951 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-4205.
When was CVE-2026-23951 published?: CVE-2026-23951 was published on 2026-01-22 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:sumatrapdfreader:sumatrapdf:-:*:*:*:*:*:*:*

More vulnerabilities in Sumatrapdfreader Sumatrapdf

CVE-2012-4896 — Critical (CVSS 9.3): Heap-based buffer overflow in SumatraPDF before 2.1 allows remote attackers to execute arbitrary code via a crafted PDF…
CVE-2012-4895 — Critical (CVSS 9.3): Heap-based buffer overflow in SumatraPDF before 2.1 allows remote attackers to execute arbitrary code via a crafted PDF…
CVE-2009-4117 — Critical (CVSS 9.3): Multiple stack-based buffer overflows in pdf_shade4.c in MuPDF before commit 20091125231942, as used in SumatraPDF…
CVE-2026-23512 — High (CVSS 8.6): SumatraPDF is a multi-format reader for Windows. In 3.5.2 and earlier, there is a Untrusted Search Path vulnerability…
CVE-2026-25880 — High (CVSS 7.8): SumatraPDF is a multi-format reader for Windows. In 3.5.2 and earlier, the PDF reader allows execution of a malicious…
CVE-2012-5340 — High (CVSS 7.8): SumatraPDF 2.1.1/MuPDF 1.0 allows remote attackers to cause an Integer Overflow in the lex_number() function via a…

All CVEs affecting Sumatrapdfreader Sumatrapdf →

Other CWE-193 (Off-by-one Error) vulnerabilities

CVE-2024-10442 — Critical (CVSS 10.0): Off-by-one error vulnerability in the transmission component in Synology Replication Service before 1.0.12-0066,…
CVE-2026-53309 — Critical (CVSS 9.8): In the Linux kernel, the following vulnerability has been resolved: ocfs2/dlm: fix off-by-one in dlm_match_regions()…
CVE-2024-38441 — Critical (CVSS 9.8): Netatalk before 3.2.1 has an off-by-one error and resultant heap-based buffer overflow because of setting ibuf[len] to…
CVE-2023-46853 — Critical (CVSS 9.8): In Memcached before 1.6.22, an off-by-one error exists when processing proxy requests in proxy mode, if \n is used…
CVE-2023-38429 — Critical (CVSS 9.8): An issue was discovered in the Linux kernel before 6.3.4. fs/ksmbd/connection.c in ksmbd has an off-by-one error in…
CVE-2022-34970 — Critical (CVSS 9.8): Crow before 1.0+4 has a heap-based buffer overflow via the function qs_parse in query_string.h. On successful…

Browse all CWE-193 (Off-by-one Error) vulnerabilities →