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Advisory severityMedium4.8Red Hat Linux

Medium [CVE-2026-63984] fix hdrlen overflow in ipv6_rpl_srh_decompress

This medium-severity Red Hat Linux advisory covers CVE-2026-63984 affecting Red Hat Enterprise Linux 10.0 Extended Update Support, Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions, Red Hat Enterprise Linux 9.6 Extended Update Support.

Aggregated and source-linked by VulniPulse. Data sources, validation and limitations.

CVE-2026-63984 Source published Source updated

VulniPulse record published Record updated

CVE-2026-63984
Affected products & platforms
Red Hat LinuxLinux Kernel
Open source advisory

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Summary

In the Linux kernel, the following vulnerability has been resolved: ipv6: rpl: fix hdrlen overflow in ipv6_rpl_srh_decompress() ipv6_rpl_srh_decompress() computes: outhdr->hdrlen = (((n + 1) * sizeof(struct in6_addr)) >> 3); hdrlen is __u8. For n >= 127 the result exceeds 255 and silently truncates.

With n=127 (cmpri=15, cmpre=15, pad=0, hdrlen=16): (128 * 16) >> 3 = 256, truncated to 0 as __u8 The caller in ipv6_rpl_srh_rcv() then places the compressed header at buf + ((ohdr->hdrlen + 1) 255, which prevents n+1 from overflowing unsigned char (the segments_left field), but does not prevent the computed hdrlen from overflowing __u8. n=127 passes because 128 127.

This caps n at 126, giving hdrlen = (127 * 16) >> 3 = 254, which fits in __u8. The compressed header then lands at buf + ((254 + 1) << 3) = buf + 2040, exactly past the decompressed region (buf[0..2039]).

127 segments is well beyond any realistic RPL deployment. A flaw was found in the Linux kernel's IPv6 Routing Protocol for Low-Power and Lossy Networks (RPL) segment routing header (SRH) decompression function, ipv6_rpl_srh_decompress().

An integer overflow occurs when processing a specially crafted IPv6 packet, causing the header length calculation to truncate. This vulnerability could allow a remote attacker to cause data corruption.

An integer truncation in the IPv6 RPL SRH decompression path can make h…

Affected versions

No affected-version range was extracted from the source record. The vendor advisory is authoritative. Check it before change work.

Official advisory · high-confidence parse· fetched 7 days ago·verify at source

Fixed versions
  • kernel-0:6.12.0-211.63.1.el10_2
  • kernel-0:6.12.0-55.111.1.el10_0
  • kernel-0:5.14.0-687.55.1.el9_8
  • kernel-0:5.14.0-427.154.1.el9_4
  • kernel-0:5.14.0-570.147.1.el9_6
  • RHSA-2026:76738
  • RHSA-2026:83707
  • RHSA-2026:76739
  • RHSA-2026:77218
  • RHSA-2026:77219

Official advisory · high-confidence parse· fetched 7 days ago·verify at source

Mitigation checklist

Recommended fix / mitigation
  • Mitigation for this issue is either not available or the currently available options don't meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.

Official advisory · high-confidence parse· fetched 7 days ago·verify at source

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