LiveActive security incident?Get immediate response
CVE Record

CVE-2020-36791: net_sched: keep alloc_hash updated after hash allocation

In the Linux kernel, the following vulnerability has been resolved: net_sched: keep alloc_hash updated after hash allocation In commit 599be01ee567 ("net_sched: fix an OOB access in cls_tcindex") I moved cp->hash calculation before the first tcindex_alloc_perfect_hash(), but cp->alloc_hash is left untouched. This difference could lead to another out of bound access. cp->alloc_hash should always be the size allocated, we should update it after this tcindex_alloc_perfect_hash().

UnknownCVSS not scoredNot KEV-listedUpdated
Discuss exposureBack to CVEs
Glexia's TakeAutomated analysisunknown

Security readout for executives and security teams

Plain-English summary

This Linux kernel issue is an out-of-bounds access risk in network scheduling code. It was introduced around earlier cls_tcindex hash handling and resolved by keeping the recorded allocation size synchronized after hash allocation. Public sources provide no CVSS score and no KEV evidence of active exploitation.

Executive priority

Handle through normal kernel patch governance unless local exposure analysis shows vulnerable custom or lagging kernels. There is no provided severity score or active exploitation evidence, but kernel memory safety issues deserve timely remediation.

Technical view

The bug is in net_sched cls_tcindex. After moving cp->hash calculation before tcindex_alloc_perfect_hash(), cp->alloc_hash was not updated, creating a mismatch between allocated size and tracked size that could lead to another out-of-bounds access. Linux stable commits are listed as fixes across supported branches.

Likely exposure

Exposure depends on exact Linux kernel lineage and distro backports. Systems running kernels that include commit 599be01ee567 without the later stable fix may be relevant. Validate by package changelog or commit ancestry rather than version number alone.

Exploitation context

The bundle cites syzkaller and a syzbot-related blog, suggesting fuzzer discovery or reproduction context. It does not cite public exploitation, weaponized proof-of-concept activity, or CISA KEV listing. Treat exploitation status as unconfirmed.

Researcher notes

Focus analysis on cls_tcindex allocation accounting. The key condition is cp->alloc_hash not reflecting the size allocated by tcindex_alloc_perfect_hash(). The public record is patch-oriented and lacks CVSS, CWE, impact detail, and exploitability prerequisites.

Mitigation direction

  • Update Linux kernels using vendor or distribution-supported packages.
  • Confirm the relevant stable fix commit is present or backported.
  • Prioritize custom kernels and older stable branches for review.
  • Monitor Linux and distribution advisories for corrected package versions.
  • Avoid deploying unsupported kernels without backported stable fixes.

Validation and detection

  • Inventory Linux kernel versions and package build identifiers.
  • Check distro changelogs for CVE-2020-36791 or listed fix commits.
  • For custom kernels, verify ancestry includes the relevant stable commit.
  • Confirm no production hosts remain on affected custom builds.
  • Record KEV status as not listed in the supplied bundle.
Prepared
Confidence
medium
Sources
11

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cve · low confidence lookup

CVE-2020-36791 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

Open ATT&CK lookup
Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
3Timeline events
0ADP providers
10Source links

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux73c29d2f6f8ae731b1e09051b69ed3ba2319482b, b974ac51f5834a729de252fc5c1c9de9efd79b45, 6cb448ee493c8a514c9afa0c346f3f5b3227de85, 478c4b2ffd44e5186c7e22ae7c38a86a5b9cfde5, dd8142a6fa5270783d415292ec8169f4ea2a5468, 2c66ff8d08f81bcf8e8cb22e31e39c051b15336a, 599be01ee567b61f4471ee8078870847d0a11e8eunaffected
LinuxLinux4.4.214, 4.9.214, 4.14.171, 4.19.103, 5.4.19, 5.5.3unaffected
Weakness

CWE details

No CWE listed

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.