VulnerabilityPublished 13 Aug 2026Updated 29 Oct 2026

CVE-2026-30922: Dvc · Denial of Service in pyasn1 via Unbounded Recursion

Affects dvcSource GCVE Database

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Not known to be exploited · CVSS 7.5 High : upgrade to 3.67.0_1 soon.

Data as of 30 Oct 2026, 06:59 UTC

CVSS 3.0 base score

7.5High

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.8% chance of exploitation in 30 days – higher than 57% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 3.67.0_1

CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: None
Availability: High

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 13 Aug 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade dvc to 3.67.0_1.

Patches and advisories

Affected software

Product	Affected	Fixed in
Homebrewdvc`pkg:brew/dvc`Other threats	Affected >=0.63.4 <3.67.0_1	Fixed in 3.67.0_1

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

Description

### Summary The `pyasn1` library is vulnerable to a Denial of Service (DoS) attack caused by uncontrolled recursion when decoding ASN.1 data with deeply nested structures. An attacker can supply a crafted payload containing nested `SEQUENCE` (`0x30`) or `SET` (`0x31`) tags with Indefinite Length (`0x80`) markers. This forces the decoder to recursively call itself until the Python interpreter crashes with a `RecursionError` or consumes all available memory (OOM), crashing the host application. ### Details The vulnerability exists because the decoder iterates through the input stream and recursively calls `decodeFun` (the decoding callback) for every nested component found, without tracking or limiting the recursion depth. Vulnerable Code Locations: 1. `indefLenValueDecoder` (Line 998): ```for component in decodeFun(substrate, asn1Spec, allowEoo=True, **options):``` This method handles indefinite-length constructed types. It sits inside a `while True` loop and recursively calls the decoder for every nested tag. 2. `valueDecoder` (Lines 786 and 907): ```for component in decodeFun(substrate, componentType, **options):``` This method handles standard decoding when a schema is present. It contains two distinct recursive calls that lack depth checks: Line 786: Recursively decodes components of `SEQUENCE` or `SET` types. Line 907: Recursively decodes elements of `SEQUENCE OF` or `SET OF` types. 4. `_decodeComponentsSchemaless` (Line 661): ```for component in decodeFun(substrate, **options):``` This method handles decoding when no schema is provided. In all three cases, `decodeFun` is invoked without passing a `depth` parameter or checking against a global `MAX_ASN1_NESTING` limit. ### PoC ``` import sys from pyasn1.codec.ber import decoder sys.setrecursionlimit(100000) print("[*] Generating Recursion Bomb Payload...") depth = 50_000 chunk = b'\x30\x80' payload = chunk * depth print(f"[*] Payload size: {len(payload) / 1024:.2f} KB") print("[*] Triggering Decoder...") try: decoder.decode(payload) except RecursionError: print("[!] Crashed: Recursion Limit Hit") except MemoryError: print("[!] Crashed: Out of Memory") except Exception as e: print(f"[!] Crashed: {e}") ``` ``` [*] Payload size: 9.77 KB [*] Triggering Decoder... [!] Crashed: Recursion Limit Hit ``` ### Impact - This is an unhandled runtime exception that typically terminates the worker process or thread handling the request. This allows a remote attacker to trivially kill service workers with a small payload (<100KB), resulting in a Denial of Service. Furthermore, in environments where recursion limits are increased, this leads to server-wide memory exhaustion. - Service Crash: Any service using `pyasn1` to parse untrusted ASN.1 data (e.g., LDAP, SNMP, Kerberos, X.509 parsers) can be crashed remotely. - Resource Exhaustion: The attack consumes RAM linearly with the nesting depth. A small payload (<200KB) can consume hundreds of megabytes of RAM or exhaust the stack. ### Credits Vulnerability discovered by Kevin Tu of TMIR at ByteDance.

References

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