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Review reviewCritical

CVE-2026-63984

Linux

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) << 3). With hdrlen=0 this is buf + 8, but the decompressed region occupies buf[0..2055] (8-byte header...

CVSS
9.8
EPSS
-
- percentile
CISA KEV
Not listed
Published
2026.07.20
PRIORITY ASSESSMENT

Review review

The CVSS severity warrants an early asset and exposure review.

Known exploitationNot established by KEV
Exploit probability-
Technical severityCVSS 9.8

Vulnerability overview

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) << 3). With hdrlen=0 this is buf + 8, but the decompressed region occupies buf[0..2055] (8-byte header...

Affected product and versions

Product
Linux
Affected versions
>= 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 < 75b3680047bf09af8e7e471a7a6ddf2ce5847f56, >= 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 < fd238c51b0fa5390cceca9f1ac5a9ffda8063eed, >= 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 < 3618b34942b76471d044369bfd30d58c39068bf1, >= 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 < 97e06791368c01f0ad2a4b3269c2abe19485ca32, >= 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 < de02fc049352af5a9595f015511222d0a85c326b, >= 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 < 6fe1cb312038516cb4d9fa089d700af7059f1a64, >= 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 < c0487a9c1e116cf349e2d1f302d9019670460858, >= 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 < 9d5e7a46a9f6d8f503b41bfefef70659845f1679, >= 5.7
Fixed versions
No verified fixed-version field is available yet

Recommended response sequence

Confirm exposure before applying a vendor-supported change.

Full remediation guide
  1. 1
    Identify

    Confirm that Linux and an affected version are present.

  2. 2
    Prioritize

    Combine exploitation signals with asset exposure and business criticality.

  3. 3
    Remediate

    Follow the vendor advisory or supported update path and preserve rollback options.

  4. 4
    Verify

    Recheck the version, service health, access paths, and relevant logs.

Technical data

CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CWE
Not available
CVE-2026-63984 — Linux | SECUFOCUS NOW