libical through 4.0.6 contains a heap-based out-of-bounds read in icalvalue_decode_ical_string() in src/libical/icalvalue.c when decoding input ending in a backslash. Attackers can supply escaped iCalendar text with a trailing backslash, causing the loop to read past the terminator and crash the application or leak adjacent heap memory.
Fix
Microsoft's update · Moderate
- Release Notes — azl3 libical 3.0.10-1 on Azure Linux 3.0 · build 3.0.10-3
From the 2026-Oct release note of Microsoft's Security Update Guide, revised 2026-10-31.
Every line above is quoted from NVD, CISA, Microsoft, the vendor's own advisory or DISA; nothing is generated.
Change history 4
- References-1 references (now 7)NVD modified 2026-10-26 15:16
- References+1 references (now 7)NVD modified 2026-10-26 14:16
- StatusReceived → DeferredNVD modified 2026-10-16 18:25
- First seenCVSS 6.9NVD modified 2026-10-15 22:19
Affected (CPE criteria) 0
NVD has not attached CPE configurations yet.
References 7
- https://github.com/libical/libical
- https://github.com/libical/libical/blob/9cfca65c122fa23b9680a28e0c9225a2fd015fc5/src/libical/icalvalue.c#L1608-L1645
- https://github.com/libical/libical/commit/d753885ce2de7c105d6b8c405aa7aee1d98ad8de
- https://github.com/libical/libical/pull/1455
- https://hackmd.io/@haind-pwn/libical-icalvalue-decode-ical-string-oob-read
- https://www.vulncheck.com/advisories/libical-through-4.0.6-heap-out-of-bounds-read-via-icalvalue-decode-ical-string
- https://hackmd.io/@haind-pwn/libical-icalvalue-decode-ical-string-oob-read