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CVE Record

CVE-2026-0994: Denial of Service in Python Protobuf

A denial-of-service (DoS) vulnerability exists in google.protobuf.json_format.ParseDict() in Python, where the max_recursion_depth limit can be bypassed when parsing nested google.protobuf.Any messages. Due to missing recursion depth accounting inside the internal Any-handling logic, an attacker can supply deeply nested Any structures that bypass the intended recursion limit, eventually exhausting Python’s recursion stack and causing a RecursionError.

HighCVSS 8.2Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

Python services that convert untrusted JSON-like data into Protobuf messages may be crashed by excessively nested Any messages. The flaw bypasses the parser’s intended recursion limit, exhausting Python’s recursion stack. The documented impact is denial of service, not data theft or modification.

Executive priority

Treat internet-facing or multi-tenant parsing services as urgent because unauthenticated input may disrupt availability. Patch promptly after confirming applicability, then review parser exposure and protective limits. Lower priority is reasonable only where ParseDict() cannot receive untrusted data or Any messages are absent.

Technical view

google.protobuf.json_format.ParseDict() fails to account for recursion depth within internal Any-message handling. Nested Any structures can therefore bypass max_recursion_depth until Python raises RecursionError. The source assigns CVSS 4.0 score 8.2 and CWE-674, with high availability impact and no stated confidentiality or integrity impact.

Likely exposure

Prioritize Python applications using ParseDict() on attacker-controlled or externally supplied data containing Any messages. The bundle lists Protobuf versions through v33.4, but its default-status metadata is ambiguous; confirm applicability against the upstream record and vendor advisories rather than relying solely on version matching.

Exploitation context

The CVSS vector describes network reachability, low complexity, no privileges, and no user interaction, with an attack prerequisite. CISA KEV status is false, and the supplied sources do not establish active exploitation or public weaponization. Practical exposure depends on whether untrusted input reaches the affected parsing path.

Researcher notes

The failure is incomplete recursion accounting in the Any-specific parsing path, classified as CWE-674. Expected behavior is RecursionError after Python stack exhaustion; service-level impact depends on exception handling and process architecture. The supplied evidence does not establish code execution, confidentiality loss, integrity loss, or active exploitation.

Mitigation direction

  • Apply the corrected Protobuf package or operating-system update identified by the applicable vendor advisory.
  • Review the upstream Protobuf change and vendor guidance before selecting a target version.
  • Restrict untrusted input from reaching ParseDict() where immediate updating is unavailable.
  • Use request size, depth, timeout, and resource controls as temporary availability protections.

Validation and detection

  • Inventory Python Protobuf versions across applications, containers, build artifacts, and managed operating-system packages.
  • Identify every ParseDict() call and determine whether externally supplied data can reach it.
  • Confirm whether affected schemas accept or contain google.protobuf.Any messages.
  • Verify deployed package versions against the upstream record and applicable Red Hat errata.
  • Perform controlled regression testing for deeply nested Any input without exposing production services.
Prepared
Confidence
high
Sources
8

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

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cwe · low confidence lookup

CWE-674: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

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cve · low confidence lookup

CVE-2026-0994 mapping review

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

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Vulnerability profileCVE Program record
Severity
High
CVSS
8.2 (4.0)
Known Exploited
No
Published

Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L

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.

2CVSS vectors
5Timeline events
2ADP providers
22Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: yesTechnical Impact: partial

CVSS vector scores

2 official scores

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
8.2CVSS 4.0HighCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L——Google
7.5CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H3.93.6redhat-SADP

Vulnerability scoring details

Base CVSS 4.0 score

8.2High
CVSS 4.0 vector shape for CVE-2026-0994Attack VectorAttack ComplexityAttack RequirementsPrivileges RequiredUser InteractionVS ConfidentialityVS IntegrityVS AvailabilitySS ConfidentialitySS IntegritySS Availability

Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Attack Requirements
NonePresent
Privileges Required
NoneLowHigh
User Interaction
NonePassiveActive
VS Confidentiality
HighLowNone
VS Integrity
HighLowNone
VS Availability
HighLowNone
SS Confidentiality
HighLowNone
SS Integrity
HighLowNone
SS Availability
HighLowNone

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. ADP timelineredhat-SADP

    Made public.

  3. CVE publishedCVE Program

    The CVE record was published.

  4. ADP timelineredhat-SADP

    Reported to Red Hat.

  5. CVE updatedCVE Program

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

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc
redhat-SADPpython: protobuf: Protobuf: Denial of Service due to recursion depth bypass
other:Red Hat severity ratingcvssV3_1
  • 2026-01-23T16:02:59.235Z: Reported to Red Hat.
  • 2026-01-23T14:55:16.876Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
PythonProtobuf<=v33.4unaffected
Weakness

CWE details

CWE-674

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

CWE-674 · source CWE mapping

Uncontrolled Recursion

Uncontrolled Recursion represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs